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                            <div style="color:gray; word-break: break-all; font-size:12px;">原英文版地址: <a href="https://www.elastic.co/guide/en/elasticsearch/reference/7.7/mapping-fields.html" rel="nofollow" target="_blank">https://www.elastic.co/guide/en/elasticsearch/reference/7.7/mapping-fields.html</a>, 原文档版权归 www.elastic.co 所有<br/>本地英文版地址: <a href="../en/mapping-fields.html" rel="nofollow" target="_blank">../en/mapping-fields.html</a></div>
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<strong>重要</strong>: 此版本不会发布额外的bug修复或文档更新。最新信息请参考 <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/index.html" rel="nofollow">当前版本文档</a>。
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<span class="breadcrumb-link"><a href="index.html">Elasticsearch Guide [7.7]</a></span>
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<span class="breadcrumb-node">Meta-Fields</span>
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<a href="mapping-field-names-field.html"><code class="literal">_field_names</code> field »</a>
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<h2 class="title">
<a id="mapping-fields"></a>Meta-Fields<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/mapping/fields.asciidoc">edit</a>
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<p>Each document has metadata associated with it, such as the <code class="literal">_index</code>, mapping
<a class="xref" href="mapping-type-field.html" title="_type field"><code class="literal">_type</code></a>, and <code class="literal">_id</code> meta-fields.  The behaviour of some of these meta-fields
can be customised when a mapping type is created.</p>
<h3>
<a id="_identity_meta_fields"></a>Identity meta-fields<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/mapping/fields.asciidoc">edit</a>
</h3>
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<p>
<a class="xref" href="mapping-index-field.html" title="_index field"><code class="literal">_index</code></a>
</p>
</td>
<td valign="top">
<p>
The index to which the document belongs.
</p>
</td>
</tr>
<tr>
<td valign="top">
<p>
<a class="xref" href="mapping-type-field.html" title="_type field"><code class="literal">_type</code></a>
</p>
</td>
<td valign="top">
<p>
The document’s mapping type.
</p>
</td>
</tr>
<tr>
<td valign="top">
<p>
<a class="xref" href="mapping-id-field.html" title="_id field"><code class="literal">_id</code></a>
</p>
</td>
<td valign="top">
<p>
The document’s ID.
</p>
</td>
</tr>
</tbody>
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<h3>
<a id="_document_source_meta_fields"></a>Document source meta-fields<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/mapping/fields.asciidoc">edit</a>
</h3>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<a class="xref" href="mapping-source-field.html" title="_source field"><code class="literal">_source</code></a>
</span>
</dt>
<dd>
The original JSON representing the body of the document.
</dd>
<dt>
<span class="term">
<a href="https://www.elastic.co/guide/en/elasticsearch/plugins/7.7/mapper-size.html" class="ulink" target="_top"><code class="literal">_size</code></a>
</span>
</dt>
<dd>
The size of the <code class="literal">_source</code> field in bytes, provided by the
<a href="https://www.elastic.co/guide/en/elasticsearch/plugins/7.7/mapper-size.html" class="ulink" target="_top"><code class="literal">mapper-size</code> plugin</a>.
</dd>
</dl>
</div>
<h3>
<a id="_indexing_meta_fields"></a>Indexing meta-fields<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/mapping/fields.asciidoc">edit</a>
</h3>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<a class="xref" href="mapping-field-names-field.html" title="_field_names field"><code class="literal">_field_names</code></a>
</span>
</dt>
<dd>
All fields in the document which contain non-null values.
</dd>
<dt>
<span class="term">
<a class="xref" href="mapping-ignored-field.html" title="_ignored field"><code class="literal">_ignored</code></a>
</span>
</dt>
<dd>
All fields in the document that have been ignored at index time because of
<a class="xref" href="ignore-malformed.html" title="ignore_malformed"><code class="literal">ignore_malformed</code></a>.
</dd>
</dl>
</div>
<h3>
<a id="_routing_meta_field"></a>Routing meta-field<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/mapping/fields.asciidoc">edit</a>
</h3>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<a class="xref" href="mapping-routing-field.html" title="_routing field"><code class="literal">_routing</code></a>
</span>
</dt>
<dd>
A custom routing value which routes a document to a particular shard.
</dd>
</dl>
</div>
<h3>
<a id="_other_meta_field"></a>Other meta-field<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/mapping/fields.asciidoc">edit</a>
</h3>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<a class="xref" href="mapping-meta-field.html" title="_meta field"><code class="literal">_meta</code></a>
</span>
</dt>
<dd>
Application specific metadata.
</dd>
</dl>
</div>








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